1. Field of the Invention
The present invention relates to an anti-theft system that can be applied to a propellant such as a vehicle that is propelled by an engine (internal combustion engine) installed thereon (e.g., a motorcycle, an ocean vessel, a jet propulsion boat, etc.). In particular, the invention relates to a propellant anti-theft system that is simplified in its system configuration and operation.
2. Description of the Related Art
In the past, when an engine of a vehicle or the like is started, one can turns on a key switch for engine starting in a mechanical manner with the use of a cylinder key that is possessed only by an authorized driver. Accordingly, it is impossible to start the engine without the use of a qualified key, which serves to achieve a vehicle anti-theft effect. However, even if the vehicle anti-theft function is achieved by depending upon the key, which can be reproduced relatively easily, so a satisfactory anti-theft effect can not necessarily be achieved.
Accordingly, there has been proposed a system in which to strengthen the anti-theft effect, information for specifying or identifying a key of the vehicle of concern is transmitted from the key to a key cylinder, so that the transmitted information from the key is identified on the side of the key cylinder, and a permission to start the engine is given only when the transmitted information indicates normal information (see, for example, a first patent document: Japanese examined patent application publication No. H4-15141).
In the above-mentioned known system, an annular core with a rotor coil being wound therearound is arranged in the periphery of a keyway or key insertion hole in the key cylinder, and a shaft-like core with a key coil being wound therearound is arranged in the interior of the key with the shaft-like core being arranged near the annular core to form a pair of magnetic circuits, whereby information for driving the engine is sent and received between the key and the key cylinder through the magnetic circuits.
In the known propellant anti-theft system, a certain anti-theft effect can be obtained as stated above but there is a problem that satisfactory security can not be achieved.
In addition, there is also another problem that no preventive measure exists against theft of the vehicle at the time when the driver inadvertently left the vehicle with the key being kept inserted in the key cylinder.
Moreover, although it can be considered that a lamp is installed on the key cylinder in view of the fact that when the engine is started at night, the keyway in the key cylinder can not be found easily in the dark and it takes time to start the engine, there is a restraint on the design of a driver's seat and therearound due to the existence of the key cylinder, and besides the installation of the lamp on a relatively inexpensive propellant such as a motorcycle, etc., leads to an increase in costs, and hence such a measure is not practical.
Further, there is still another large problem that various parts such as an ignition control unit, a fuel control unit, meters, a steering locking section and so on might be stolen after the vehicle has been destroyed.